Engine Hesitation and MPG

evildragon · #1 03-11-2007, 01:25 AM

Ok, two things. On a 94 Chevy Caprice Classic LS, what can cause engine hesitation? It only happens at low RPMs..

ALSO, what is the supposed MPG for this car? Me and my teacher in my tech college did a calculation on it, my car is pulling off 9.6 MPG, which seems pathetic really.. (possibly related to the above?)

EDIT: It seems to be less hesitant when the engine is cold too.. Like, if it's cold outside and I start driving it, it runs great..

1968 Pontiac · #2 03-11-2007, 07:09 PM

Have you checked the coolant temperature sensor? If it's skewed it still works, but gives your computer the wrong temperature, so your car could be running rich all the time. If you have a scanner, you can check the temp reading, or you can check the sensor with an ohm meter. I just don't know where the sensor is on an LT1.

evildragon · #3 03-11-2007, 07:22 PM

Quote:

Originally Posted by 1968 Pontiac

Have you checked the coolant temperature sensor? If it's skewed it still works, but gives your computer the wrong temperature, so your car could be running rich all the time. If you have a scanner, you can check the temp reading, or you can check the sensor with an ohm meter. I just don't know where the sensor is on an LT1.

i don't have a scanner, but i do have a multimeter.. i can probably find this sensor with the service manual (my service manual tends to not actually show "where" to look for something, but just shows "how")

EDIT: You know, I just noticed that the temp gauge on the dash stays in the Cold area, even when driving to school on a hot day...

1968 Pontiac · #4 03-12-2007, 07:11 PM

Be sure you are checking the CTS, as there is also an engine temp sensor for your gauge on the dash. The CTS tells the computer what to do; the ETS only gives a readout to the gauge.

You may also have a problem with your thermostat being stuck open. You may want to look at replacing it.

fabchef · #5 03-15-2007, 11:05 PM

evil..i've been having the same problem with my 96 9c1 L99 engine. I had remembered the guy who had the car before me, tell me that a week before, the engine cooling temp. sensor (the one on the water pump), had failed and the car ran like crap and smoked alot. He changed it with a used one he had on his other caprice. My can would run okay on cold start but at running temp, it would hesitate at idle and when i would shift in and out or gears it would stall at times.
Today i checked the sensor and it seemed a little rough, i looked at the connector terminals for the sensor and it was rusted and coroded inside.
I went to gm and got a new sensor and hookup wire for it (the wire costed more than the sensor!!!). Anywho after soldering and taping the wires properly, i installed the new sensor and the car runs much better, no stumbling and there is no more smell of raw fuel outside the car. I filled up my tank to see if my consumptioon, so far it seems a bit better.
NOTE: if you disconnect the sensor while the car is running both the fans should kick in around 20-30 sec. later..good way to see if they work..good luck..
oh ya, the sensor and wire costed about 100 canadian dollars...
fabs

jefhaz · #6 03-25-2007, 06:29 PM

My 1989 was acting very mcuh as described. I replaced the CTS and the early results are good. Thanks for the tips!

evildragon · #7 03-27-2007, 12:31 AM

now I just have to find where the CTS is, and how to test it.. my service manual just don't show it..

Blue Bowtie · #8 03-27-2007, 08:31 AM

HINT: It's the only electrical connector you see in this photo (not counting spark plug wires) :

FWIW, US EPA mileage is 17/25 for the LT1, 18/25 for the L99.

The resistance of the temperature sensor should be close to what is indicate in the table at a known temperature.

Since the dash gauge also indicates a relatively low coolant temperature, I'd suspect the thermostat as well. The lower disc of the two-tier thermostat can have a tendency to fall off after about ten years and a couple million miles. Don't mess around with a lower temperature unit. Get the factory 180ºF thermostat if you replace it.

evildragon · #9 03-27-2007, 06:21 PM

i just checked the resistance.. for 80F, it read 2580...

evildragon · #10 04-01-2007, 01:32 AM

um, one more question... how do I check the temperature when the car is on?

I have an IR thermometer that I can use to check the engine temp.. But do I just disconnect it for resistance while the car is running? Cause I would think that would damage something as then the computer doesn't know ANY temp, and has infinite resistance (to the computer anyway, as it's then an open circuit)

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